1. Field of the Invention
The present invention relates generally to overhead garage doors, and more particularly, to a safety device to prevent the overhead door from moving downward in the event of a failure in tension of a control cable.
2. Description of the Prior Art
The use of both manually operated and power operated overhead garage doors is well known in the art. In addition, special apparatus to deal with certain unsafe conditions associated with such overhead garage doors are also known.
For example, U.S. Pat. No. 3,958,367 of Fairman discloses an overhead garage door that has elongated coil springs to substantially balance the door weight for ease of opening the door. A safety device is provided in the event that a coil spring breaks. The safety device employs an elongated flexible member that extends longitudinally axially through the elongated springs and substitutes for the spring in the event that the spring breaks. The extent to which the door moves after breakage of a spring depends upon the extent of stretching that the elongated flexible safety member undergoes after the spring breaks. Moreover, if a control cable breaks, the door will not be restrained from rapidly moving downward.
U.S. Pat. No. Des. 262,939 of Shook et al discloses a safety locking device for garage doors which includes a hinged flap.
U.S. Pat. No. 4,269,253 of Ziegler discloses a garage door with safety guards installed over the gaps between hingedly connected horizontal panels to prevent fingers from being caught between the horizontal panels.
U.S. Pat. No. 4,640,049 of Duncan discloses a safety device for overhead garage door counterbalance springs. A flexible safety cable extends through the open center of the spring and is anchored at each end to the garage structure. The safety cable is placed under sufficient tension to contain the spring against horizontal or vertical movement in the event that the spring breaks. The extent to which the door moves after breakage of a spring depends upon the extent of stretching that the flexible safety cable undergoes after the spring breaks. Moreover, if a control cable breaks, the door will not be restrained from rapidly moving downward.
U.S. Pat. No. 4,757,853 of Price discloses a safety device for garage door springs that are used to couterbalance the weight of the door. An elongated flexible member extends longitudinally through each of the coil springs and is anchored at each end to fixed supports. If spring breaks, broken portions of the spring will be retained on the elongated flexible member. The extent to which the door moves after breakage of a spring depends upon the extent of stretching that the elongated flexible member undergoes after the spring breaks. Moreover, if a control cable breaks, the door will not be restrained from rapidly moving downward.
U.S. Pat. No. 4,956,938 of DeMent discloses a safety device for a power operated overhead door which is operated by wire control cables for raising and lowering the door. A cam plate having a toothed edge is pivotably moved to instantaneously clamp or bind against the wire control cable to stop its downward movement in the event that any obstacle such as a small child, is detected in the path of the door while it is being closed. However, the cam plate is biased to permit the wire control cable to move in a direction to open the door even after the safety device is actuated. Moreover, if a control cable breaks, the door will not be restrained from rapidly moving downward.
Thus, while the foregoing body of prior art indicates that it is well known to use safety devices to protect against damage or injury from broken counterbalance springs, that it is well known to grab a tensioned control cable to prevent an overhead door from moving lower onto a sensed child who stands under the door, and that it is well known to guard against a person's fingers being caught between adjacent horizontal panels of an overhead garage door, the provision of a simple and cost effective device for automatically halting downward movement of an overhead garage door, in the event that tension in a control cable is abruptly lost, is not disclosed.
In this respect, the prior art described above does not teach or suggest the provision of a simple and cost effective device for automatically halting downward movement of an overhead garage door in the event that tension in a control cable is abruptly lost device due to either breakage in a counterbalance spring or breakage in the control cable. The foregoing disadvantages are overcome by the unique overhead door safety apparatus of the present invention as will be made apparent from the following description thereof. Other advantages of the present invention over the prior art also will be rendered evident.